let _Vue = null
export default class VueRouter {
    static install(Vue) {
        // 1.判断当前插件是否安装
        if (VueRouter.install.installed) {
            return
        }
        VueRouter.install.installed = true
        // 2.把Vue构造函数记录到全局变量
        _Vue = Vue
        // 3.把创建的vue实例的时候传入的router对象注入到Vue实例上
        // 混入
        _Vue.mixin({
            beforeCreate() {
                if (this.$options.router) {
                    _Vue.prototype.$router = this.$options.router
                }

            }
        })
    }
    constructor(options) {
        this.options = options
        this.routeMap = {}
        // 创建响应式对象
        this.data = _Vue.observable({
            current: '/'
        })
    }
    init() {
        this.createRouteMap()
        this.initComponents(_Vue)
        this.initEvent()
    }
    createRouteMap() {
        this.options.routes.forEach(route => {
            this.routeMap[route.path] = route.component
        })
    }
    initComponents(Vue) {
        Vue.component('router-link', {
            props: {
                to: String
            },
            render(h) {
                return h('a', {
                    attrs: {
                        href: `#${to}` //hash路由
                    },
                    on: {
                        click: this.clickHandler
                    }
                }, [this.$slots.default])
            },
            methods: {
                clickHandler(e) {
                    // 实际逻辑
                    window.location.hash = `#${to}`
                    this.$router.data.current = this.to
                    e.preventDefault()
                }
            }
        })
        const self = this
        Vue.component('router-view', {
            render(h) {
                const component = self.routeMap[self.data.current]
                return h(component)
            }
        })
    }
    initEvent(){
        window.addEventListener('hashchange', () => {
            this.data.current = window.location.hash.substr(1)
        })
    }
}